Solar thermal tube plate heat exchanger

ABSTRACT

A combination solar absorber and atmospheric radiator in multiple embodiments, a method for constructing these embodiments, and a method for using the combination solar absorber and atmospheric radiator, the absorber/radiator has a thermally conductive sheet which serves as a back plate, tubular fluid conduit or conduits, generally rectangular thermally conductive caps, and a means for fastening the caps to the sheet, covering one or more conduits and pressing them against the sheet. The side of the sheet with the caps and conduits is exposed to the sun and atmosphere, providing two thermal pathways to and from the conduit.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 60/809,878, filed May 31, 2006, the teachings of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to solar thermal tube-plate heatexchangers.

The external surface of buildings receives solar energy. Most of thereceived solar energy is transferred passively to the building byheating up the walls, the roof and other exposed external surfaces ofthe building. Roofs and walls face the sky, protect against the sun, thecold and the rains, but roofs and walls make little use of the sun, thenight's coolness or evaporative cooling. Some have taken advantage ofthe available solar energy by developing devices that actively harnessthe solar radiation. Solar flat-plate collectors are one example of suchdevices.

Flat plate thermal solar collectors have been developed to takeadvantage of the available solar radiation for heating purposes. Suchcollectors mostly include one or more fluid-filled tubes arranged on aheated plate. The tube-plate heat exchange surface is also usuallyplaced in an enclosure. The enclosures have a clear glass, referred toas glazing, to allow solar radiation to reach the tube-plate arrangementwithin the collector's enclosure. While flat-plate collectors enjoy arich history of use, they are none-the-less susceptible to certainshortcomings. One such shortcoming is the loss of solar energy due tolosses of the incoming radiation to the glazing as well as otherstructures of the solar collectors. Another loss in efficiency inflat-plate collectors is due to the presence of sharp temperaturegradients which afflict flat-plate collectors near the tubes. Anotherdisadvantage of flat-plate collectors is that the tube-plate surfaceneeds protection from wind and rain and other elements. As suchflat-plate collectors have sturdy enclosures, which detract from theiroverall thermal efficiency and add to their mounting and fasteningdemands.

Therefore there still exists a need to more effectively harness theroofs and walls of buildings for heat exchange applications and also fora tube-plate type heat exchanger that can take advantage of theavailable solar energy while not suffering from the above-describedshortcomings.

BRIEF SUMMARY OF THE INVENTION

The present invention provides an apparatus having a generally flatthermally conductive sheet which serves as a back plate; tubular fluidconduit or conduits (rubber or plastic tubes or hoses, or metal pipes)generally as long as either the length or the width of the sheet, thetubular fluid conduit or conduits containing fluid (water or alternativefluid commonly used for such an apparatus, for example containinganti-freeze); and generally rectangular thermally conductive cap orcaps, the cap or caps having lengths and widths appropriate for coveringone or more of the tubular fluid conduit or conduits; and a means forfastening each cap to the sheet; the caps fastened to that side of thesheet which is exposed to the sun or atmosphere; thereby covering one ormore of the tubular fluid conduit or conduits and pressing them againstthe sheet. The caps if used in plurality need not be contiguous to eachother, but could be arranged on the sheet so as to leave space betweenthem, exposing part of the sheet to the sun or atmosphere. The sheet andthe cap or caps may be made of any metal such as copper or aluminum, aswell as steel or any combination of these materials. For example, copperand/or aluminum caps may be used on a steel sheet. The tubular fluidconduit or conduits may be made of any heat resistant rubber such assantoprene, silicone or ethylene-propylene-diene monomer (epdm), or anyheat resistant plastic such as polypropylene or polyethylene, or a metalsuch as copper or aluminum, or any combination of these materials. Forexample, both copper and santoprene tubular fluid conduit or conduitscan be used on different parts of the embodiment of the apparatus.

In operation, the apparatus in accordance with one embodiment of thepresent invention is deployed by exposing to the sun or atmosphere theside of the sheet onto which the tubular fluid conduit or conduits arefastened by the cap or caps, providing two thermal pathways to and fromthe conduits. A first pathway is from the plate to the conduit, and asecond pathway is from the cap to the conduit. As a solar absorber, anyparticular embodiment of the apparatus functions when solar energy heatsthe cap, the cap then conducts the heat to the portion of the tubularfluid conduit or conduits beneath the cap, where the heat warms theportion of the tubular fluid conduit or conduits beneath the cap,subsequently warming the fluid in the tubular fluid conduit or conduits;and when solar energy heats the exposed portion of the sheet, the sheetthen conducts the heat to the area of the sheet underneath the tubularfluid conduit or conduits, where the heat warms the portion of thetubular fluid conduit or conduits adjacent to the sheet, subsequentlywarming the fluid in the tubular fluid conduit or conduits. As anatmospheric radiator, every embodiment of the apparatus functions whenheat conducts from the fluid in the tubular fluid conduit or conduits tothe portion of the tubular fluid conduit or conduits adjacent to thesheet and then to the unexposed portion of the sheet that is covered bythe tubular fluid conduit or conduits and cap, the heat then migratingto the exposed portion of the sheet not covered by a cap, where the heatis then radiated to the atmosphere; and when heat conducts from thefluid in the tubular fluid conduit to that portion of the tubular fluidconduit or conduits adjacent to the cap and then to the cap, where theheat is then radiated to the atmosphere.

It is an unexpected advantage of the various embodiments of theapparatus that it is not necessary to use optimally thermally conductivematerials for any particular embodiment of the apparatus to operateeffectively. Fastening tubular fluid conduit or conduits and caps closetogether to a large area of a relatively poorly conductive sheet canoften provide sufficient heat transfer to and from the sheet. By tightlyenclosing the tubular fluid conduit or conduits and fastening them tothe sheet, the contact of the tubular fluid conduit or conduits with thecap or caps and the sheet is optimized.

Although the apparatus in accordance with the embodiments of the presentinvention can collect or radiate the most heat from a given area of roofor wall, the demand may be less than what the building can supply. Inmany cases it is more economical to space the tubular fluid conduits farapart across the entire roof or wall than to place them close togetheron a part of it. Instead of investing in 1,000 feet of tubes or hoses orpipes which would then be spaced 6 inches apart across a roof or wall of0.032 inch aluminum, it is more economical to use only 800 feet of tubesspaced 12 inches apart. Placement of tubular fluid conduit or conduitson metal roofs and walls is guided by getting the most energy with theleast additional expense. The heat exchangers of radiator/absorbers thatare described herein can use the roofs and walls of buildings and thusthe investment in metal skin, back insulation and support structure hasbeen made before using the roof or wall to give or take heat. Theadditional use of the wall or roof by adding metal caps, tubular fluidconduit or conduits and headers is much less expensive than the totalcost of the usual solar absorbers or radiators.

The cap or caps provide numerous additional benefits to the embodimentsof the apparatus. By mechanically constraining a tubular fluid conduitor conduits, they are prevented from runaway expansion if the fluid inthem freezes, since a tubular fluid conduit is more prone to aneurysm ifits radius has expanded; e.g., see U.S. Pat. No. 5,143,053 (Baer).Because the cap or caps can be fastened to the sheet with relative ease,such as by threaded fasteners, adhesives and epoxies, rivets, soldering,welding, nailing and snapping-on, the embodiments of the apparatus arevery easy to construct or modify in the field as well as in the shop.The cap or caps improve the efficiency of the embodiments of theapparatus, for when the caps carry heat parallel to the plate below,they lessen the steep temperature gradient that afflicts other platecollectors near the tubular fluid conduit or conduits. It is notnecessary for the cap or caps to be in thermal contact with the sheet;even without such thermal contact, a cap absorbs or dissipates heat thatwould otherwise have to be absorbed or dissipated by the area of thethermally conductive sheet in contact with the tubular fluid conduit orconduits.

A fastening means has been implemented by the cap or caps with C-shapedcross-sections transversely of the elongated direction, wherein theC-shaped cap or caps are snapped-on to ridges raised from or attached tothe sheet. In addition to ease of attachment, the fastening means hasthe benefit in regard to heat transfer of approximating tapered finseven if the caps are not in thermal contact with the sheet. Inembodiments where the ridges are not only raised or attached but alsoconvex and undercut, upon fastening a C-shaped cap to the ridge, theridge goes into compression, and the cap goes into tension and grips theridge tighter.

Some of the benefits of using plastic or rubber tubes or hoses are thatthey are inexpensive, they readily conform to the cap or caps, and theycan be rapidly cut to proper length on site. Polyethylene is inexpensiveand thermally conductive. Because plastic and rubber tubes are sold inrolls of flat tube, they do not take up space at the work place. Rubbertubes in particular are freeze tolerant, but the tubular fluid conduitor conduits utilized generally do not need to be freeze tolerant. Theinventors herein have found that the flexing of the metal or steel sheetand cap provides freeze protection where the metal is 26 gauge steel.

Some embodiments, such as those deployed on roofs, can avoid freezing,due to the drain back of the fluid; whenever a freeze threatens, thewater drains out of the absorber and into storage.

For a further understanding of the nature and advantages of theinvention, reference should be made to the following description takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a front and side elevation view of an embodiment of theapparatus wherein the caps have outwardly curving flanges on thecross-section, which caps are attached by either screws or adhesive, andthe side of the sheet on which the caps are attached is exposed to thesun.

FIG. 2A shows a front and side elevation view in detail of an embodimentof the apparatus using two different designs of caps, which are fastenedto the sheet with screws or adhesive.

FIG. 2B shows a front and side elevation view in detail of thecross-section of an embodiment of the apparatus using two differentdesigns of caps, both of which are fastened to the sheet with screws oradhesive.

FIG. 3A shows a side elevation view in detail of an embodiment of theapparatus using a cap having a single bend and outwardly curving flangeson the cross-section, fastened to a sheet using screws.

FIG. 3B shows a side elevation view in detail of an embodiment of theapparatus using a cap having a single bend and outwardly curving flangeson the cross-section, fastened to a sheet using adhesive.

FIG. 3C shows a side elevation view in detail of an embodiment of theapparatus using a cap having two bends and outwardly curving flanges onthe cross-section, fastened to a sheet using screws.

FIG. 3D shows a side elevation view in detail of an embodiment of theapparatus using a cap having two bends and outwardly curving flanges onthe cross-section, fastened to a sheet using adhesive.

FIG. 3E shows a side elevation view in detail of an embodiment of theapparatus using a cap having a C-shaped cross-section transversely ofthe elongated direction with inwardly curving flanges, fastened to asheet having raised and undercut ridges.

FIG. 3F shows a side elevation view in detail of an embodiment of theapparatus using a cap having a C-shaped cross-section transversely ofthe elongated direction with inwardly curving flanges, fastened to asheet having raised, undercut and convex ridges.

FIG. 3G shows a side elevation view in detail of an embodiment of theapparatus using a cap having two bends and inwardly curving flanges onthe cross-section, fastened to a sheet having raised and undercutridges.

FIG. 4A shows a front elevation view of a sheet having raised, undercutridges.

FIG. 4B shows a side elevation view of a sheet having raised, undercutridges.

FIG. 4C shows a front elevation view of a sheet having raised, undercutand convex ridges.

FIG. 4D shows a side elevation view of a sheet having raised, undercutand convex ridges.

FIG. 5A shows a front and side elevation view of an embodiment of theapparatus as an integral part of a roof.

FIG. 5B shows a side elevation view of an embodiment of the apparatus asan integral part of a roof.

FIG. 5C shows a front and side elevation view of an embodiment of theapparatus as an integral part of a roof wherein the headers areconcealed in the eaves.

FIG. 6A shows a front and side elevation view of an embodiment of theapparatus deployed as a panel on a roof.

FIG. 6B shows a side elevation view of an embodiment of the apparatusdeployed as a panel on a roof.

FIG. 7A shows a front and side elevation view of an embodiment of theapparatus as an integral part of a wall.

FIG. 7B shows a side elevation view of an embodiment of the apparatus asan integral part of a wall.

FIG. 7C shows a side elevation view of the hot and cold fluid lines asthey enter the fluid reservoir.

FIG. 8A shows a front and side elevation view of an embodiment of theapparatus as a panel that is attached to a wall.

FIG. 8B shows a side elevation view of an embodiment of the apparatus asa panel that is attached to a wall.

FIG. 9A shows a front elevation view of an embodiment of the apparatusas a panel that does not need to lie on a roof or wall.

FIG. 9B shows a side elevation view of an embodiment of the apparatus asa panel that does not need to lie on a roof or wall.

FIG. 9C shows a front elevation view of an embodiment of the apparatusdeployed horizontally in three short rows.

FIG. 9D shows a front elevation view of an embodiment of the apparatusdeployed vertically in two short rows.

REFERENCE NUMERALS FOR DRAWINGS

-   10 Generally flat thermally conductive sheet;-   12 Fastening means consisting of screws;-   14 Fastening means consisting of adhesives;-   20 Tubular fluid conduit or conduits;-   30 Cap or caps having outwardly curving flanges on the    cross-section;-   31 Cap or caps having inwardly curving flanges on the cross-section;-   32 Caps having a C-shaped cross-section transversely of the    elongated direction with inwardly curving flanges;-   35 Bend in the cap;-   40 Undercut ridge raised from or attached to the sheet;-   50 Undercut, convex ridge raised from or attached to the sheet;-   60 Roof;-   64 Silicone tube;-   68 Eaves;-   70 Wall;-   80 Embodiment of the apparatus as a panel;-   90 Fluid reservoir;-   100 Shutters;-   120 Hot fluid line;-   125 Cold fluid line;-   130 Top of an embodiment of the apparatus 140;-   140 An embodiment of the apparatus;-   150 Top of the fluid reservoir 90;-   160 Bottom of the fluid reservoir 90;-   170 Bottom of an embodiment of the apparatus 140;-   180 Rise in the cold fluid line 125;-   190 Vacuum breaker riser;-   200 Upper header;-   210 Lower header;-   220 Fin;-   230 Mullion; and-   240 Horizontal slat.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of the apparatus uses flexible thin wall plastic orrubber tubes or hoses (which more generally are types of “tubular fluidconduit or conduits”) pressed against the metal roof or walls of abuilding to gain heat from the sun in the day or dispose of heat to theatmosphere at night. A heat exchange fluid, such as water flows throughthe tubes by convection, or is pumped, to pick up solar heat during theday or to give out heat at night. Metal caps flatten, squash orotherwise securely fasten the tubes against the metal of the building.For an existing metal roof or metal sidewall, the caps can be heldagainst the flattened tubes by adhesive such as silicone sealant. For anew metal roof or metal sidewall, the metal of the building can beformed in a series of raised sections with undercuts along the sides sothat a cap may mechanically snap in place.

The skins of most metal buildings are poor heat conductors. Most metalbuildings are actually made of steel, typically painted 26 gauge (0.0179inch thick) steel or 29 gauge (0.0135 inch thick) steel. For such skinsto serve well as collectors or radiators, the tubes with flowing watershould ideally be within an inch or two of where the sun strikes. Oneinch tubes, when flattened, become 1⅜ inches wide. This is a significantadvance in the design of flat plate collectors of the unglazed variety,which are particularly sensitive to poor thermal conduction of steel. Itis fortunate that flattening or squashing the tubes makes them wider andthe spaces between narrower.

The caps transfer heat to or from the flowing water in the tubes. Thecap presses against the top or outside of the tube, while the metal roofor wall touches the underside of the tube. Sun striking the cap passesheat through the top of the tube. Sun striking the spaces between capspasses heat a longer distance to the bottom of the tube. In all flatplate collectors, the hottest point is about half way between tubes. Ifmade of the same material, the sections of metal roof exposed betweencaps are hotter than the caps. These parts of the roof would be hotterand less efficient without the caps. The caps carry much of the heatthat the roof would otherwise have to carry. The caps which wereintroduced to flatten the tubes against the roof act as thermalconductors as well. In one implementation, for the caps and underlyingmetal to work, the caps could intercept approximately half the sun andoccupy half the space between it and the adjacent cap. Caps and roofeven of the same metal can stress adhesive bonds as temperatures change.For this reason, if attached by adhesives, caps should be of relativelyshort lengths overlapping each other. Any heat transfer directly fromcap to the building, and vice versa, through an adhesive on actualcontact is welcome and increases efficiency, but it is unnecessary forgood performance.

A dramatic demonstration of the efficiency of the cap and roof was madeby flipping an assembly frontside-back, so a roof panel must transferall the heat to the tube and the cap merely clings in the shade below.Efficiency dropped dramatically.

Other advantages of the cap and roof arrangement include variable flowcross section and freeze tolerance. When the caps, which are eitherglued or snapped, are made shallow, they squash the rubber or plastictube almost flat, making the tube wide but also reducing its crosssections. This is an advantage, provided sufficient flow can occur.

Another feature of the cap is the potentially large contact area betweenflowing water and tube in direct contact with a metal heat conductor.When the space between cap and roof is 0.1875 inch, then a 1 inchdiameter, 3.14 inch circumference tube has 2.55 inches of itscircumference in contact with metal. If the tubes are 3 inches oncenter, there is a wet area in direct contact with metal comprising 85%of the area struck by the sun. If the tubes are 4 inches on center, thenthe sun strikes 69% of this area. This large area reduces thetemperature differential between flowing water and tube, and isespecially critical where sluggish thermosyphon flow restricts heattransfer at the interface.

A wall that thermosphyons to a water reservoir above it can have shallowcaps and thus flattened tubes. There are large elevation differences andrelatively large temperature differences to drive circulation with solarheating. Shallow caps can also be used with pumped flow. Wherethermosyphon flow through almost horizontal roofs is used to cool waterat night, larger flow channels are required. Here, the caps must bedeeper, and the tubes have larger cross-sections. Another reason to havewell flattened tubes for winter solar heating on walls is the freezingof water. The less ice that forms, the less heat is required the nextday to melt it. Walls may be used to cool at night. This requirespumping if the thermal mass is above the wall.

Another advantage of using metal caps is that metal can flex when thewater in the tubes freezes. Ice breaks water pipes because it expands8%. Flexible tubes flattened between metal caps and a metal roof expandwhen ice forms. The metal flexes allowing the ice to expand but returnsto the original volume when the ice melts. A 26 gauge, 1.5 inch wide, ⅛inch deep cap, attached to a 26 gauge metal roof, flexes enough to allowthe freeze thaw cycle at 10 psi. A cap only 3/32 inch deep would handlestill greater pressure because the less the volume to freeze, the lessthe stress on the metal and its means of attachment.

Absorbers that freeze need to be able to expand, and then contract onthawing. Elasticity can be provided by rubber waterways such assilicone, santoprene or ethylene-propylene-diene monomer (epdm), by themetal cap and roof flexing or by a combination. Thin wall polyethyleneis well suited as a waterway since a thickness such as 0.015 inchimposes only a small temperature change through the tube wall. Tofacilitate installation of the tubes, the tubes can be evacuated of airand thereby flattened.

The absorber/radiator in accordance with the embodiments of the presentinvention, which may have deep caps and large cross section tubes whenused in roof radiators, does not need to withstand freezing for it canbe drained the entire winter or at least during winter nights. Duringfreeze thaw cycles an absorber need not necessarily withstand an entire8% increase in volume if excess water can retreat from the freezing zoneas freezing occurs. A roof collector used for passive summer cooling anddrain back heating such as that described in U.S. Pat. No. 6,357,512need not be freeze tolerant. In practice, care should be taken duringfreezing to allow some liquid to escape from the freezing zone as iceforms.

FIG. 1 shows a front and side elevation view of an embodiment of theapparatus wherein the caps have outwardly curving flanges on thecross-section, which caps are attached by either screws or adhesive, andthe side of the sheet on which the caps are attached is exposed to thesun. The embodiment of the apparatus shown in FIG. 1 includes agenerally flat thermally conductive sheet 10, tubular fluid conduit orconduits 20 fastened to the sheet 10 by a thermally conductive cap orcaps 30. The thermally conductive sheet 10 and the thermally conductivecap or caps 30 can be made of any metal such as copper or aluminum, orof steel. The tubular fluid conduit or conduits can be made of rubber,plastic or metal, such as santoprene, silicone, polypropylene,polyethylene, ethylene-propylene-diene monomer, aluminum or copper. Thetubular fluid conduit or conduits 20 are fastened to the sheet 10 bythermally conductive caps 40. As disclosed in the summary, the cap orcaps can be fastened to the sheet by threaded fasteners such as screws12 and nuts and bolts, adhesives 14 and epoxies, rivets, soldering,welding, nailing and snapping-on. A snapping-on fastening means isdisclosed in FIGS. 3E and 3F below.

The cap or caps 30 have been made each with as few as one bend andtypically with two bends, not counting the bends used to form outwardly-and inwardly-curving flanges. Embodiments where the cap 30 is a shallowV-shape cannot generally be walked on without disturbing or destroyingthe embodiment of the apparatus, since a force as would be exerted bywalking on the embodiment might snap the cap loose or break it loose iffastened by adhesive. A flat cap, in contrast, would not move sidewaysunder such a force. Such V-shaped embodiments, however, are functional,and may be used on walls 70.

FIG. 2A shows a front and side elevation view in detail of an embodimentof the apparatus using two different designs of caps, which are fastenedto the sheet with screws or adhesive. FIG. 2B shows a front and sideelevation view in detail of the cross-section of an embodiment of theapparatus using two different designs of caps, both of which arefastened to the sheet with screws or adhesive. FIGS. 2A and 2B showseveral types of caps 30 and fasteners. FIG. 2A shows a cap 30 with asingle bend not counting the bends is used to form outwardly- andinwardly-curving flanges, and caps 30 with two bends. The caps 30 arefastened to the sheet 10 with either adhesive 14 or screws 12. FIG. 2Bshows cross-sections of two types of caps 30, including those with botha single bend 35 and those with two bends 35. Both types of caps 30 inFIGS. 2A and 2B have outwardly curving flanges 31 on the cross-section.

FIG. 3A shows a cap 30 having a single bend 35 not counting the bendsused to form outwardly- and inwardly-curving flanges, wherein the cap 30is fastened to the sheet 10 using screws 12. FIG. 3B shows a cap 30having a single bend 35, wherein the cap 30 is fastened to the sheet 10using adhesive 14. FIG. 3C shows a cap 30 having two bends 35, whereinthe cap 30 is fastened to the sheet 10 using screws 12. FIG. 3D shows acap 30 having two bends 35, wherein the cap 30 is fastened to the sheet10 using adhesive 14. FIG. 3E shows a cap having a C-shapedcross-section transversely of the elongated direction 32, attached to aridge 40 that is undercut and raised from the sheet 10. As shown in FIG.3F, with a raised and undercut ridge that is also convex 50, then whenthe ridge or ridges 50 go into compression, the cap or caps 32 moretightly grip the ridge or ridges 50 than with a non-convex ridge. FIG.3G shows a flat-topped cap 30 and a flat-topped ridge 50; in such aconfiguration, the flexing is most comfortable.

FIG. 4A shows an undercut ridge 40 raised from the sheet 10. FIG. 4Bshows a sheet 10 having an undercut, convex ridge 50 raised from orattached to the sheet 10.

FIG. 5 shows that the sheet 10 is a metal roof 60 over a house or otherstructure, providing to the inside of the structure a thermallycontrolled environment. For an existing metal or steel roof 60, the caps30 and tubes are fastened in a pattern that conforms to the existingridges of the corrugation. For a new 0.0179 inch (26 gauge) steel roof60, the roof 60 is roll formed with 0.125 inch deep raised, undercutridges 40 spaced every 4 inches, pressing a ⅞ inch inner diameter 0.015inch wall polyethylene tube 20 between a 2 inch wide cap 30 and the roof60. For a new 0.032 inch aluminum roof 60, the roof 60 is roll formedwith 0.1875 inch deep raised, undercut ridges 40 spaced every 6 inches,pressing a ⅞ inch inner diameter 0.015 inch wall polyethylene tube 20between a 3 inch wide cap 30 and the roof 60. When using caps having atleast ¼ inch outwardly curving flanges, the caps 30 are glued on to thesteel or aluminum below. When using caps having a C-shaped cross-sectiontransversely of the elongated direction with inwardly curving flanges32, the caps 32 are snapped on to the raised, undercut ridges.

The sheet 10 and the caps 30 are made with 0.0179 inch (26 gauge) steel(with a thermal conductivity of 26 BTUs per degrees F. per foot perhour), because a human can generally walk on it without damaging theroof 60 or the embodiment of the apparatus 140 and because the materialsare relatively inexpensive. Steel has relatively poor thermalconductivity, but the embodiment of the apparatus will work despite poorthermal conductivity. Other embodiments are constructed with an aluminum(with a thermal conductivity of 128 BTUs per degrees F. per foot perhour) sheet 10 and caps 30. The tubular fluid conduit or conduits 20consist of ⅞ inch inner diameter, 0.015 inch wall polyethylene (with athermal conductivity of 0.20 BTUs per degrees F. per foot per hour). Athinner walled plastic tubing is preferred, because the heat transfer isbetter due to a smaller temperature drop across the tube wall.

The cross-section of the tubular fluid conduit 20 varies by the pitch ofthe roof 60. Shallow roofs 60 require larger flow channels, thereforelarger cross-section tubes 20, for easier flow.

An example of this embodiment is as the radiator/absorber for U.S. Pat.No. 6,357,512 (Baer and Mingenbach), which is a passive solar thermalcontrol system that utilizes a roof 60. Such embodiment utilizes upper200 and lower 210 headers, one at each of the terminal ends of thetubular fluid conduit or conduits 20. The most cost effective method ofconnecting the silicone tube 64 to the header 200, 210 is by simplemechanical puncture of the header 200, 210 by the silicone tube 64.Because fluid will be lost though the silicone tubes 64, extra largeheaders 200, 210 are used so that they also serve as expansion tanks.Because of this fluid loss, the system needs annual refilling.

FIG. 5C shows an embodiment wherein the upper headers 200 are concealedunder the roof 60 and lower headers 210 are concealed in the eaves 68.The upper headers 200 are concealed from view by connecting the tubularfluid conduit or conduits 20 at their lower ends to silicone tubes 64 inwhich a ninety degree bend is formed such that the silicone tube 64 maypass through a hole 66 in the roof 60 and connect to an upper header200. The lower headers 210 are concealed from view by connecting thetubes 20 at their lower ends to silicone tubes 64 in which a ninetydegree bend is formed such that the silicone tube 64 may pass under theeaves 68 and connect to a lower header 210.

As shown in FIG. 6, an embodiment of apparatus 140 is alternativelybuilt as a panel 80 on a roof 60, rather than as an integral part of theroof 60 as in FIGS. 5A-C.

As shown in FIG. 7, it is possible to deploy an embodiment of theapparatus as an integral part of a wall 70 rather than a roof 60. Thewall 70 will work better for heating, rather than cooling. South-facingwalls 70 are preferred, due to their solar exposure. Because of thesteep elevation gradients and temperature gradients that will occurwithin a vertical configuration, wall deployments of embodiments of theapparatus should have smaller cross-section tubes 20 to reduce thevolume of fluid. The smaller cross-section tubular fluid conduit orconduits 20 also lessens the thaw-out time in the morning. Because walls70 will not be walked on, the shallow V-shaped cap 30 with a single bendmay be used; generally, less robust materials and configurations can beused on walls 70.

One embodiment of the wall 70 is similar to that as disclosed in U.S.Pat. No. 6,357,512 (Baer and Mingenbach), for which an embodiment of theapparatus serves as the radiator/absorber that is named in the patent,but which radiator/absorber is deployed in a vertical position in amanner described below. A fluid reservoir 90 is situated near theceiling 100 above the space to be cooled or heated 110. A hot fluid line120 runs from the top 130 of the embodiment of the apparatus 140, whichembodiment of the apparatus 140 is deployed as a vertical panel on thewall 70, to the top 150 of the fluid reservoir 90. A cold fluid line 125runs from the bottom 160 of the fluid reservoir 90 to the bottom 170 ofthe embodiment of the apparatus 140. To prevent siphoning the water backout of the fluid reservoir 90 if the fluid pressure is lost, thewell-known technique is used that involves raising 180 the cold fluidline 125 as it leaves the fluid reservoir 90 to the level of the top ofthe fluid reservoir 90, that is, above the water line, and adding ananti-siphon hole 190 at the raised point 170.

As shown in FIG. 8, an embodiment of the apparatus 140 is built as apanel 80 that is then deployed on a wall 70, rather than building theapparatus 140 into the wall 70 itself as in FIG. 7.

FIG. 9 shows an embodiment of the apparatus 140 in the form of a heatcollecting fin 220 used in flat plate collectors. Such a fin 220 doesnot need to lie on a roof or wall. There is a saving of approximatelytwenty-five percent in fin material with no loss in efficiency ascompared to fins with constant cross sections. FIG. 9 shows an eightinch wide, 0.040 inch aluminum sheet as a back plate 10, with a fiveinch wide, 0.040 inch aluminum cap 30 fastened around a three-quarterinch copper pipe as the fluid conduit 20. This system had the sameperformance as an eight inch wide snap-on 0.070 inch thick aluminumextrusion which weighed twenty-five percent more.

FIG. 9 shows two ways in which this embodiment is deployed, namely inone or two long lines or many short rows, either horizontally (FIG. 9C)or vertically (FIG. 9D). This flexibility allows the collector to bedesigned to suit the space available to it. In the horizontalconfiguration the heat collecting fins can be cut to fit betweenmullions 230 or (their equivalents if windows are not used, e.g.,vertical slats) with pipes strapped into place. With sufficient mullion230 depth they can be rotated on the tubes to provide seasonal lightadjustment as well as optimum collection angle. They can also be mounteddirectly to the mullions 230. In the vertical configuration they can becut to fit horizontal slats 240.

Some advantages of the embodiments of the apparatus were previouslyenumerated above. Every advantageous feature does not need to beincorporated into every embodiment of the apparatus and/or methods.

All publications and descriptions mentioned above are hereinincorporated by reference in their entirety for all purposes. None isadmitted to be prior art.

The above description is illustrative and is not restrictive, and as itwill become apparent to those skilled in the art upon review of thedisclosure, the present invention may be embodied in other specificforms without departing from the essential characteristics thereof.These other embodiments are intended to be included within the scope ofthe present invention. For example, the cap or caps could be fastened tothe thermally conductive sheet by pierce tags or by buckles, and thetubes and caps and ridges could run diagonally or at other angles acrossthe roof or wall. The scope of the invention should, therefore, bedetermined not with reference to the above description, but insteadshould be determined with reference to the following and pending claimsalong with their full scope or equivalents.

1. An apparatus for absorbing heat from the sun and dissipating heat tothe atmosphere at night; said apparatus comprising: a generally flatthermally conductive sheet which serves as a back plate; one or moretubular fluid conduit or conduits; a generally rectangular thermallyconductive cap for covering and pressing said conduit or conduitsagainst said sheet; said cap having a length and a width generallycovering the one or more of said conduit or conduits; said cap notcovering the entire sheet if used in plurality; said cap not contiguousto each other in the parallel if used in plurality; and a means forfastening the thermally conductive cap to said thermally conductivesheet; thereby covering said one or more conduit or conduits andpressing them against said sheet; said cap fastened to that side of saidsheet which is exposed to the sun and atmosphere.
 2. The apparatus ofclaim 1 wherein said thermally conductive sheet or thermally conductivecap are made of steel.
 3. The apparatus of claim 1 wherein saidthermally conductive sheet or thermally conductive cap are made of ametal selected from the group consisting of aluminum, copper, andcombinations thereof.
 4. The apparatus of claim 1 wherein said tubularfluid conduit or conduits are made of a plastic material selected fromthe group consisting of polyethylene and polypropylene.
 5. The apparatusof claim 1 wherein said tubular fluid conduit or conduits are made of arubber material selected from the group consisting of silicone,santoprene, ethylene-propylene-diene monomer (epdm), and combinationsthereof.
 6. The apparatus of claim 1 wherein said tubular fluid conduitor conduits are made of a metal selected from the group consisting ofaluminum, copper, and combinations thereof.
 7. The apparatus of claim 1wherein said cap has an outwardly or inwardly curved flange on thecross-section transversely of the elongated direction.
 8. The apparatusof claim 7 wherein said thermally conductive sheet or thermallyconductive cap are made of steel.
 9. The apparatus of claim 7 whereinsaid thermally conductive sheet or thermally conductive cap are made ofa metal selected from the group consisting of aluminum, copper, andcombinations thereof.
 10. The apparatus of claim 7 wherein said tubularfluid conduit or conduits are made of a plastic selected from the groupconsisting of polyethylene and polypropylene.
 11. The apparatus of claim7 wherein said tubular fluid conduit or conduits are made of a rubberselected from the group consisting of silicone, santoprene,ethylene-propylene-diene monomer (epdm), and combinations thereof. 12.The apparatus of claim 7 wherein said tubular fluid conduit or conduitsare made of a metal selected from the group consisting of aluminum andcopper.
 13. The apparatus of claim 7 wherein said means for fasteningcomprises a generally rectangular thermally conductive cap having aC-shaped cross-section transversely of the elongated direction; andridge or ridges raised from or attached to said thermally conductivesheet; said ridge or ridges undercut transversely of the elongateddirection.
 14. The apparatus of claim 13 wherein said raised andundercut ridge or ridges are convex.
 15. The apparatus of claim 13wherein said thermally conductive sheet or thermally conductive cap aremade of steel.
 16. The apparatus of claim 13 wherein said thermallyconductive sheet or thermally conductive cap are made of a metalselected from the group consisting of aluminum, copper, and combinationsthereof.
 17. The apparatus of claim 13 wherein said tubular fluidconduit or conduits are made of a plastic selected from the groupconsisting of polyethylene and polypropylene.
 18. The apparatus of claim13 wherein said tubular fluid conduit or conduits are made of a rubberselected from the group consisting of silicone, santoprene orethylene-propylene-diene monomer (epdm).
 19. The apparatus of claim 13wherein said tubular fluid conduit or conduits are made of a metalselected from the group consisting of aluminum, copper, and combinationsthereof.
 20. A method for using a thermally conductive sheet to gainheat from the sun in the day or to dispose of heat at night; said methodcomprising: utilizing a cap or caps to press a tubular fluid conduit orconduits containing fluid against said thermally conductive sheet;exposing to the sun or atmosphere that side of the sheet onto which thetubular fluid conduit or conduits are fastened by said cap or caps; andallowing said fluid to flow through said tubular fluid conduit orconduits by convection; or pumping said fluid to pick up solar heat orto give out heat during the night.
 21. The method of claim 20 whereinsaid thermally conductive sheet or thermally conductive cap or caps aremade of steel.
 22. The method of claim 20 wherein said thermallyconductive sheet or thermally conductive cap or caps are made of a metalselected from the group consisting of aluminum, copper, and combinationsthereof.
 23. The method of claim 20 wherein said tubular fluid conduitor conduits are made of a plastic selected from the group consisting ofpolyethylene and polypropylene.
 24. The method of claim 20 wherein saidtubular fluid conduit or conduits are made of a rubber selected from thegroup consisting of silicone, santoprene or ethylene-propylene-dienemonomer (epdm).
 25. The method of claim 20 wherein said tubular fluidconduit or conduits are made of a metal selected from the groupconsisting of aluminum, copper, and combinations thereof.